In general, the art involving electrically operated valves for handling pressurized gases is highly developed and a large number of designs have been known for many years and have long been in successful operation. Many competing designs are available in the marketplace and such designs have been successfully modified for application to a wide variety of specific uses. This art has, however, developed primarily in connection with relatively large valves, such as valves adapted for connection to conduits of at least about 1/4 inch internal diameter (1/8 NPT pipe) and arranged for supplying, for example, air cylinders of one inch in diameter and having a stroke of up to 8 inches.
However, in addition to the foregoing, there has over the past several years been developing a series of applications for electrically operated valves for controlling a pressurized gas, which valves are extremely small and are adapted for supplying a very small load, such as an air cylinder of 3/8 - 1/2 inch in diameter and having a stroke of up to 3 inches. Inasmuch as the cylinder to be so supplied is very small, the valve by which it is to be supplied should be correspondingly small. Nevertheless, for reasons of uniformity in design, convenient commercial availability of pipe, resistance to physical damage, and to minimize pressure drop from one end of a conduit to another, the line through which such valve and cylinder is supplied should be as large as possible and in any case seldom less than 1/8 NPT pipe (0.265 inch internal diameter and 0.406 external diameter).
While many valves have been offered to the market over the past several years for meeting these conditions, and some of them have been accepted and used, the valves previously available have at best been only partially satisfactory. Specifically, they have in general been reasonably successful in operation but they have been based on the designs of larger valves and when made in small sizes have often produced extremely awkward and consequently expensive manufacture and assembly problems and further they have often not been well adapted to accepting conduit in the minimum size above indicated. This can be readily understood when it is appreciated that the valves through which this art has primarily developed, such as a valve which has been offered to the industry for a substantial period of time under U.S. Pat. No. 3,251,378 or U.S. Pat. No. 2,912,009, wherein said valves are of the order of 43/8 inches long by 15/8 inches in diameter including the valve portion, create serious design problems when same are reduced to a size approximately 1 inch in diameter, or 1 inch square, and 2- 3/64 inch in length.
One particularly difficult problem in the provision of valves of small sizes, related to but separate from the foregoing, is the problem of manufacturing tolerances in that tolerances which can be accepted and which present no great difficulty in the manufacture, assembly or operation of a relatively large valve have a serious and often adverse effect on the assembly and operation of a very small valve. On the other hand, to reduce the manufacturing tolerances materially will excessively increase the cost of the manufacturing operation. It is therefore necessary to arrange a small valve in such a manner that normal manufacturing tolerances can be accepted, and the variations resulting therefrom absorbed, without creating assembly or operating problems.
A further problem involved in the design of such small valves, as aforesaid, arises out of the fact that it is for some uses desirable to provide in valves of physically small size the operating characteristics of the larger valve. For example, in providing control panels for the manufacture of small articles such as semiconductors or watches, the processing machine though complex is relatively small and hence it is undesirable to have the large control system which would be required by the use of large valves. Thus, a substantial need exists and has existed for a long time for valves with a capacity and capability for use with pipe sizes characteristic of large valves but which are themselves of much smaller size and improved electrical operating specification than previously considered necessary.
A still further problem exists with previously known valves in that the magnetism remaining in the operating components following the de-energization of the solenoid winding was often such that a relatively strong spring would be required to overcome such magnetism and effect such mechanical retraction of the operator as was necessary to effect or permit corresponding shifting of the valve. Such spring then required a substantial solenoid for overcoming same upon energization thereof and this required sufficient current in-rush at the time of such energization as to make low voltage systems, as 24 volts, of doubtful reliability. Thus, it becomes highly desirable, particularly in association with the reduction in size of the valve, to provide a design which will minimize the above-mentioned residual magnetism and thereby, through making it possible to use a smaller return spring, reduce the input of energy required to actuate the valve.
Further, if a valve can be produced operable on a reduced wattage demand, for a given capacity of fluid handling, it will have obvious advantages in reducing the size of electrical components within the valve and reducing the size, complexity and expense of the external control equipment required.
Accordingly, the objects of the invention include:
1. To provide an electrically operated valve for controlling the flow of a pressurized gas, which valve will be efficient and reliable and can be economically produced in very small sizes. PA1 2. To provide a valve, as aforesaid, which when produced in the very small sizes indicated will still be sturdy and reliable over a long period of time of high-speed repetitive operation. PA1 3. To providde a valve, as aforesaid, of construction which, even though made in the very small sizes aforesaid, will still be economical to manufacture and efficient in operation. PA1 4. To provide a valve, as aforesaid, which in spite of its very small size can be efficiently associated with conduits of sizes normally used for larger valves. PA1 5. To provide a valve, as aforesaid, which in spite of its very small size will have the performance characteristics, including capacity, of previously known larger valves. PA1 6. To provide a valve, as aforesaid, which will provide a complete internal flux path whereby to minimize flux resistance and thereby to permit increased tolerance to voltage variations. PA1 7. To provide a valve, as aforesaid, in which the residual magnetism existing after the energization of the solenoid will be reduced from previously known valves whereby to permit the use of a smaller return spring and thereby to permit its energization with a smaller amount of energy input as compared to previously known valves of similar capacity. PA1 8. To provide a valve, as aforesaid, which is well adapted for operating on either an a.c. or d.c. supply. PA1 9. To provide a valve, as aforesaid, which by simple plugging of selected ports and appropriate arrangement of piping thereto can be readily caused to operate in a variety of different modes, such as normally closed two-way and/or three-way, normally open two-way and/or three-way, as a diverter valve conducting a pressure to a selected one of two different recipient systems and as a dual pressure selector valve conducting a selected one of two different pressure levels to a single recipient system. PA1 10. To provide a valve, as aforesaid, in which all fluid lines thereto connect therewith at only one end of said valve whereby to make possible a convenient and neat connection of said valve into a fluid pressure system.